This invention relates to the field of surface treatment devices. More particularly, it relates to devices which incorporate centrifugal blasting wheels to clean, abrade or otherwise condition a surface. Such devices, such as the type manufactured by Wheelabrator-Frye, Inc. of Mishawaka, Indiana, employ abrasive particulate, such as, steel shot or grit to effect the surface treatment. In order to obtain efficient and economical operation it is necessary to recover the particulate, separate it from the debris generated by the treatment process and recycle it for further treatment.
A number of devices have been developed which incorporate a particulate throwing wheel and provide means for returning the rebounding abrasive to the throwing wheel. A particular problem with such devices is removing sand, dust, paint chips and similar debris generated by the blasting process. Failure to do so adversely affects the equipment and reduces the efficiency of the device. In the prior art various methods have been used to effect separation of shot from debris as, for example, the use of air wash separators and the use of rotating magnetic drums to attract the ferromagnetic particulate. Exemplary of the magnetic drum devices are U.S. Pat. Nos. 3,934,373 and 3,858,359, both of which are assigned to the present assignee. These devices employ a rotating nonmagnetic drum with a plurality of magnets positioned behind the drum for the purposes of attracting ferromagnetic abrasive to the drum whereby rotation of the drum conveys the attracted abrasive to a recovery means.
A problem encountered with devices of this type is the tendency of debris to intermingle or otherwise adhere to the ferromagnetic particulate and thus be carried along resulting in an undesirable accumulation of debris in the surface treatment apparatus.
It is accordingly an object of the present invention to provide an improved abrasive recovery system for a surface treatment device.
A further object of the invention is to provide an improved shot recovery system which includes means for positively separating abrasive from debris.
A further object of the invention is to provide a magnetic drum type separator which employs air under pressure to remove any nonmagnetic debris which is intermingled with the magnetic shot attracted to the drum.
Another object of the invention is to provide an improved surface treatment device which efficiently and affirmatively separates debris from shot so that the shot may be reused.
A further object of the invention is to provide an improved surface treatment device in which there is provided primary and secondary debris removal systems, the primary system removing the majority of debris while the secondary system removing debris which is intermingled with the recovered shot.
Other objects and advantages of the invention will be apparent from the remaining portion of the specification.